The implantation of materials of different types in the human or animal body in order to replace bone portions which have been worn out or which have deteriorated due to diseases of other reasons is steadily increasing. In order to eliminate the risk of having immunological diseases different synthetic materials have come into use within this technical field. As examples of suitable materials used for said purpose there can be mentioned a metal like titanium and minerals and ceramics such as high-purity alumina, tricalcium phosphate and calcium aluminate. In the absence of risks of immunological diseases fragments from natural bone may also be considered in this respect. Especially preferred materials are, however, materials having a chemical composition and crystal structure similar to those of the materials that are built up by the living organism, such as calcium hydroxyapatite. One synthetic material of this type which has come into use for restoring bone tissue is the polycrystalline mineral calcium hydroxyapatite and particularly the non-resorbable type thereof which has the formula Ca.sub.10 (PO.sub.4).sub.6 (OH).sub.2 and which is also one of the main constituents of the bones in the body wherein the organic matrix of the bone tissue is received. Said material serves as a "climb structure" for bone tissue and prevents connective tissues from growing into the region of the bone which has been destroyed and is to be restored.
Calcium hydroxyapatite of the above-mentioned formula is manufactured by Asahi Optical Co., Ltd., Tokyo, Japan, and is marketed under the trade mark APACERAM.RTM., which may be registered in some or all of the designated states. The material is available as performed pieces, such as tooth roots, bones for the middle ear and elements for brain surgery and also as a raw material in the form of blocks, which can be worked by sawing, milling and boring and which are of different shapes and porosities, and as a particulate material in the form of granules, i.e. particles of regular or irregular shapes, the sizes of which are of the orders from 0.1 mm to some millimeters. The blocks are used for large implants, preferably after having been properly shaped, and the granules are used for filling bone cavities as well as in combination with said blocks. Thus, since calcium hydroxyapatite is a hard and brittle material as most ceramics are, it is difficult to impart to the blocks the exact shapes needed for the actual implantations, by cutting or otherwise working the blocks, and therefore said granules are used in combination with the shape block pieces to fill out gaps or spaces existing between the shaped block pieces and the surrounding intact bone tissues.
In most cases the above-mentioned granules or particles are mixed with blood or a physiological saline solution in order to obtain a mass that is easier to apply to the desired site of the bone and to eliminate surface tension phenomena when applying said granules or particles to the bone. A major drawback to this material or technique is, however, that such a mass is not easily properly confined within the bone cavity referred to. Furthermore, when the mass has been applied to the bone, blood that may come from adjacent bleeding portions of the body or any other secreted body fluid will dilute the particulate mass and may even carry away the material from the site of application.
The primary object of the present invention is to overcome last-mentioned drawbacks and to provide an implant material which can be easily and consistently applied to the desired site of action, i.e. where the bone tissue restoration is to be made. More specifically, this means that the new implant material according to the present invention is capable of resisting dilution and any forces tending to carry away the material from the place of application.
These advantages with the present invention will be explained more in detail below as will also other objects of the invention as well as additional advantages therewith.